The linear relation given by the Hagen-Poiseuille equation, Eq. (1.20), is reminiscent of Ohm's law for current as a function of voltage in a current-carrying wire,

\[I=\frac{V}{\Omega}\]

where \(I\) is the current, \(V\) is the voltage difference, and \(\Omega\) is the resistance. The analogy is complete here, with \(Q\), the volumetric flow rate, being similar to the current, while the pressure difference is analogous to the voltage; thus the pressure difference drives the flow just as the voltage drives the electric current. Thus

\[Q=\frac{p_{0}-p_{L}}{\Omega_{p}}\]

where \(\Omega_{p}\) is the resistance to flow. What is the expression for resistance for laminar flow problems?

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Q = = R (Po - Pi) 8L (1.20)